PROJECT SUMMARY/ABSTRACT The primary role of the Administrative Core is to coordinate research activities among the 4 Project Sites and Genomics Core. Biological research has moved well beyond the analysis of single genes or pathways. Accordingly, this program seeks to use genome-wide analysis to gain insight into the way that differences in T cell receptor (TCR) signal strength direct thymic progenitors to adopt the ?? fate, as well as how they might influence effector fate specification. To do so, we have employed genomic analysis focused initially on the cellular targets of E box DNA-binding proteins (E proteins), which regulate critical checkpoints in development of ?? and ?? T cells. Our genome-wide analysis of E protein binding sites in the last funding cycle revealed a number of critical E protein targets and cooperating transcription factors that are critical in adoption of the ?? T cell fate. We now seek to leverage those findings through the Genomics Core to assess the function of those E protein targets within our genome-wide E protein focused network and determine how they influence ?? lineage fate. The program integrates the efforts of four leaders in ?? T cell development and E protein function. Project 1 will explore the E protein targets, Tcf7 and long noncoding RNA (lncRNA) Gm15417, in orchestrating ?? lineage commitment and adoption of the IL-17 producing effector fate. Project 2 will assess the role of E protein regulated elements in controlling noncoding transcription from the TCRV? element employed by innate-like NK??T cells and the TF Egr2, which plays a critical role in orchestrating NK?? T cell development. Our program has also discovered that particular E protein family members have specific, non-redundant roles in supporting ?? T cell development and Project 3 will elucidate the mechanistic basis for their specific roles. Project 3 has also developed a pluripotent stem cell (PSC)-based human ?? T cell development model that will enable us to assess the human relevance of program findings made in animal models. Finally, Project 4 will evaluate the role of an E protein controlled lncRNA, ThymoD, in regulating T lineage commitment and how its loss results in the extinguishing of ?? fate potential in cells committed to the ?? fate. Specifically, Project 4 will also employ imaging to visualize the effect of ThymoD on the kinetics of chromosome looping during ?? T cell development, which is a critical regulator of gene expression. The Administrative Core will coordinate these activities by: 1) re- establishing a management structure; 2) facilitating the distribution of reagents; and 3) coordinating scientific interchanges between project sites and trainee visits to the Genomics Core, and as necessary other Program Laboratories. Collectively, our program promises not only to reveal novel insights into the molecular control of ?? T cell development, but will also equip a new cadre of scientists with the skills to apply integrated wet bench and bioinformatic approaches to important questions in biology.